1. Field of the Invention
This invention relates to a recording or reproducing apparatus, and more particularly to a recording or reproducing apparatus having the function of searching a recording medium for an unrecorded part of the medium where no signal has been recorded as yet.
2. Description of the Related Art
It has been known to arrange a recording/reproducing apparatus such as a VTR or the like to have a function called an end search function. The end search function is performed, under the control of a system controller, to automatically search a recording medium, such as a magnetic tape, for the end part of an existing record, or the forefront part of an unrecorded area on the magnetic tape, in cases where, for example, another record is to be recorded after the existing record on the magnetic tape.
FIGS. 1(a), 1(b) and 1(c) of the accompanying drawings show the procedure of an end search to be made by the conventional VTR. FIG. 2 shows in a flow chart a control operation on the end search. Of these figures, FIG. 1(a) shows a magnetic tape on which a video signal has already been recorded. FIGS. 1(b) and 1(c) show the positions of a recording/reproducing head in relation to the magnetic tape. The operation of the conventional VTR is described by way of example with reference to FIGS. 1(a), 1(b), 1(c) and 2 as follows:
Referring to FIGS. 1(a), 1(b) and 1(c), upon receipt of an instruction for the end search, the system controller performs the control in one of two different manners according to whether or not the recording/reproducing head is located in a position A on the magnetic tape where the video signal is recorded (hereinafter referred to as an RF recorded part):
If the head is currently located in a position B where the video signal is not recorded (hereinafter referred to as an RF unrecorded part), the VTR is set in a tape rewinding mode (hereinafter referred to as an REW travel mode) for rewinding the magnetic tape from a current stop position "a" as shown in FIG. 1(b). The end part "b" of the existing record is detected by detecting the rise of an RF signal reproduced in the REW travel mode. Upon detection of the record end part "b", the system controller sets the VTR in a stop mode to bring the travel of the magnetic tape to a stop. The end search is then completed.
In a case where the current position of the head is an RF recorded part A, the system controller sets the VTR in a fast forward mode (hereinafter referred to as an FF travel mode), as shown in FIG. 1(c). Then, the tape is caused to travel forward at a high speed from a current stop position "c". The end part "d" of the existing record is detected by detecting the fall of an RF signal reproduced in the FF travel mode. Upon detection of the record end part "d", the system controller sets the VTR in the REW travel mode. After that, the VTR is set in the stop mode when a rise "e" of an RF signal reproduced in the REW travel mode is detected, in the same manner as mentioned above, and the end search is completed.
Referring to the flow chart of FIG. 2, the end search operation of the conventional VTR is described briefly as follows: After a start is made, the flow of operation comes to a step S5a to check the current position of the head on the tape to find if the head is at the RF unrecorded part B. If not, the flow proceeds to a step S5b. At the step S5b: A fast forward action, i.e., the FF travel of the tape, begins. At a step S5c: A check is made to find if the head is at a tape end part (hereinafter referred to as the EOT). If the head is found to be at the EOT, the flow comes to a step S5e. At the step S5e: The action of an applicable mechanism is brought to a stop to bring an end search to an end. If the head is found to be not at the EOT at the step S5c, the flow proceeds to a step S5d. At the step S5d: A check is made to find if a fall of an RF signal has been detected. If so, the flow comes to a step S5f to cause the REW travel of the tape to begin.
If the head is determined, at the step S5a, to be at the RF unrecorded part B, the flow comes from the step S5a to a step S5f. At the step S5f: The REW travel of the tape is caused to begin. At a step S5g: A check is made to find if the head is at the beginning part of the tape (hereinafter referred to as the BOT). If so, the flow comes to the step S5e. If not, the flow proceeds to a step S5h. At the step S5h: A check is made to find if a rise of an RF signal has been detected. If so, the flow proceeds to a step S5i. At the step S5i: The action of the applicable mechanism is brought to a stop to bring the end search to an end. If the rise of any RF signal is found to have not been detected as yet at the step S5h, the flow comes back to the step S5g.
In the case of the conventional VTR described above, a fall of an RF signal reproduced is arranged to be detected in the FF (fast forward) travel mode. Therefore, a space at a joint part between RF recorded parts on the tape tends to be mistakenly detected as the end part of the RF recorded part. If any signal is recorded following such mistaken detection, the contents of the RF recorded part after the joint part would be lost. Such faulty recording, therefore, presents a serious problem.
Further, in the conventional VTR, the rise of a reproduced RF signal is arranged to be detected in the REW travel mode; and the end search is brought to an end by bringing the VTR into a stop mode upon detection of the rise of the reproduced RF signal. However, this arrangement makes it impossible to find by a searching action an optimum record end part for tag recording. More specifically, the search would be made to detect a point which is located before the actual record end part, i.e., on the side of the BOT. Another problem lies in that: While the tag recording is intended to be made from the end part of the existing record, the arrangement of the VTR to terminate the end search in the stop mode causes a further discrepancy in search position when the operation mode of the VTR is shifted from the stop mode to a recording standby mode for the tag recording. In addition, it has been impossible to make a confirmation as to whether the point detected is the actual end of the existing record when the stop mode is shifted to the standby mode for the tag recording.
Further, in the field of the VTR, there has been known an art for replacing a reproduced video signal with a given self oscillating image signal (called blue back, etc.) for the purpose of making a reproduced picture more easily sightable when a reproducing action on the tape comes to an unrecorded part of the tape. In making a search for an unrecorded part in this manner, the system for monitoring reproduced RF signals over a given length of time in the above-stated manner has come to require a longer monitoring period, because of the diverse reproduction modes. In other words, there are modes of varied kinds including a slow motion reproduction mode; modes of recording at different tape transporting speeds; and reproduction of a record from such a recording tape that does not permit easy tracking control, like performing a reproducing action with a VTR of the NTSC system on a tape on which signals of the PAL system are recorded. These modes necessitate a monitoring action on the reproduced RF signals over a relatively long period of time.
Further, in cases where the above-stated monitoring action is to be performed by means of a microprocessor, a limitation imposed on software arrangement sometimes prevents securing a sufficiently long period of monitoring time. Erroneous detection and faulty actions thus have resulted from an insufficient length of the monitoring time.